Method of making sheet metal heat exchangers with air centers



p 1967 e. w. GERSTUNG 3,341,925

METHOD OF MAKING SHEET METAL HEAT EXCHANGERS WITH AIR CENTERS Filed June26, 1965 r f: if 5 49% fla ATTORNEY United States Patent 3,341,925METHGD OF MAKING SHEET METAL HEAT EX- (IHANGERS WITH AIR CENTERS GeorgeW. Ger-stung, Lockport, N.Y., assignor to General Motors Corporation,Detroit, Mich, a corporation of Deiaware Filed June 26, 1%3, Ser. No.290,738 4 Claims. (Cl. 29157.3)

This invention relates to methods of making heat exchangers and moreparticularly to methods of making integral units of air center type heatexchangers from sheet metal by a folding technique.

A heat exchanger using no air centers and a method of making such anexchanger is disclosed in the United States application Ser, No. 194,594filed May 14, 1962, now Patent No. 3,258,832 in the name of George W.Gerstung. The present application pertains to structures more suitableand capable of handling a greater amount of one fluid than of another inthe heat interchange as in the case of automobile radiators throughwhich air must pass in substantial volume as compared with the morelimited volume of engine coolant.

An object of the present invention is to provide a high productionmethod of making a sheet metal heat exchanger of low cost andlightweight construction and efiicient for the transfer of heat from onefluid to another in sitnations wherein one of the fluids, such as air,is usually not as dense or capable of storing heat as the other fluid.

The object and important features of the invention will now be describedin detail in the specification and then pointed out more particularly inthe appended claims.

In the drawings:

FIGURE 1 is a plan view of part of a heat exchanger made in accordancewith the present invention, portions in layers being broken away betterto disclose the construction;

FIGURE 2 is a side view of the shown in FIGURE 1;

FIGURE 3 is an end view of a part of a sheet of metal divided intoalternating sets of air center portions and confined fluid portionspreparatory to the step of folding those portions into a stack as shownin FIGURES 1, 2 and FIGURE 4 is an elevation view of the sheet, beforefold'ng, and as shown in FIGURE 3;

FIGURE 5 is a cross-sectional view looking in the direction of thearrows 5-5 in FIGURE 1;

FIGURE 6 is an end view of the sheet shown in FIG- URES 3 and 4 beingfolded to form a stack.

In making the heat exchanger, a single sheet 10 of metal such asaluminum is formed into wide portions 12 and 14 by making slots 16 innarrow strips 18 separating the wide portions. There are two wideportions 12 alternating with sets of two wide portions 14 as indicatedin FIGURE 4. Small hinge portions 29 of metal formed from the narrowstrips 18 are left thereby to retain the integrity of the sheet 10.Ridges 22 are formed at an acute angle with the slots 16 in each of theportions 12. Each portion 14 is provided with ridges 24 of a greaterheight extending preferably, but not necessarily, at the same angle asthe ridges 22. The ridges terminate at opposite parts of peripheral marins left in the fiat on each wide portion 14. An opening 26 is formed ineach end of each wide portion 12 and 14 with a defining raised flange 28or 30 conforming with the ridges 22 or 24 as to height. It will be notedthat all ridges and flanges extend from one side of the flat sheet 10.The product, being pressed from sheet metal, in presenting a ridge 22 or24 on one of the sheets will provide a corresponding groove 22' or 2.4on the other side.

part of an exchanger The sheet is then folded into a zigzag formation asindicated by the arrows in FIGURE 3 and the partially completed stack ofFIGURE 6-, the fold lines being confined to the narrow strips 18 orhinge portions 20 and with the open ended grooves 22' of adjacent wideportions 12 in facing relation and with the closed grooves 24' ofadjacent wide portions 14 in facing relation. This places the series offlanges 28 and 30 in such relation that a continuous header is formed ateach end of the stack. In making the stack, the peripheral margin of aportion 14 is forced into contact with the peripheral margin of theadjacent portion 14 so that closed end grooves 24' of the two portionscommunicate and connect with the openings 26. It will be noted that theridges 22 extend entirely across each wide portion 12i.e.terminate at aslot Iii-but that the end ridges 22 stop short of the correspondingflange 28. Ridges 24, on the other hand, terminate short of the edges ofeach wide portion 14 or the slots 16 and the end ridges 24 join thecorresponding flange 30. Because of this arrangement, all closed grooves24 are in communication with the headers and all grooves 22' are cut offfrom them but open at their ends to the atmosphere. 7

The sheet material 10 is preferably supplied with a coating on bothsides which when subsequently heated in the stack assembly will bond ormetal fuse together the peripheral margins and facing ridges andflanges. Each header may constitute an inlet or an outlet for the liquidin the closed grooves 24' to be heated or cooled by air passing throughthe open-ended grooves 22'. Commercially available aluminum brazingsheet may be used in making the stack into a unit but other materialsmay be employed in permanently joining the portions together. After thebrazing operation, the hinge portions 20 may easily be removed.Obviously, only metal of the hinge portions 20 at the left side ofFIGURE 6 need be removed to make the heat exchanger operative.

If engine coolant is admitted to one header, it will flow through theconfined passages defined by the closed grooves 24 of the wide portions14 and be discharged from the other header. Air, in the meanwhile, maybe forced by ram effect or otherwise through the open ended passagedetermined by the air center or ridges 22 defining the grooves 22 in thewide portions 12 of the stack. The strong agitation of or turbulenceimparted to both the air and the engine coolant promotes a veryeffective heat exchange between the two fluids.

I claim:

1. A method of making a heat exchanger having opposite sides foradmitting and discharging a first fluid such as air, said methodcomprising forming wide portions alternating with narrow strips along alength of sheet metal, the said forming including holding peripheralmargins of alternate pairs of said wide portions in the flat andpressing the metal enclosed by said margins of said alternate pairs intoridges protruding from one side of said sheet and into ridges also onsaid one side and extending entirely across the other pairs of said wideportions, forming openings defined by peripheral flanges in each of saidwide portions, folding and compressing said sheet with fold lines withinsaid narrow strips into zigzag formation with the ridges and peripheralflange of each wide portion of an alternate pair into facing relationwith the ridges and peripheral flange of the adjacent wide portion ofsaid alternate pair, securing the peripheral flanges of each pair ofalternate wide portions together, and said method including the removalof sheet metal from each of said narrow strips connecting the wideportions of an alternate pair to an adjacent wide portion to open thegrooves formed by corresponding ridges.

2. A method of making a heat exchanger comprising forming a length ofsheet metal into alternate pairs of Wide portions with adjacent Wideportions separated by narrow portions, said forming comprising makingparallel ridges and grooves terminating at fiat margins for each ofalternate sets of said wide portions and parallel ridges and groovesextending the full width of the other sets of said Wide portions,bending said length Within the limits of each narrow portion to form azigzag construction, pressing and securing the flat margins of each pairof alternate wide portions together, and removing metal from one of saidnarrow portions connecting a pair of alternate wide portions to anadjacent pair of said other wide portions so that the latter may beeffective as air centers.

3. A method of making a heat exchanger comprising forming a length ofsheet metal into wide portions with adjacent Wide portions beingseparated by narrow portions, said forming comprising removing metalfrom said narrow portions to make openings through the sheet metal butleaving the length of sheet metal as an integral structure, said formingalso including making ridges defining grooves in each of said wideportions with all ridges protruding from only one side of said sheetwith the ridges in alternate pairs of said wide portions terminatingshort of the corresponding narrow portions to leave flat margins on saidalternate pairs and with the ridges in the other pairs of said wideportions extending the full width of each of the latter, folding theremaining metal of said narrow portions so that said length of sheetmaterial attains a zigzag arrangement, and pressing and securing theflat margins of each pair of alternate wide portions together and theapices of the ridges of each wide portion against the apices of anadjacent wide portion.

4. A method of making a heat exchanger as set forth in claim 3 whereinthe step of securing comprises brazing said wide portions together tomake a unitary structure defining separate paths for two fluids.

References Cited UNITED STATES PATENTS CHARLIE T. MOON, PrimaryExaminer.

CHARLES SUKALO, Examiner.

JAMES D. HOBART, S. W. MILLARD,

Assistant Examinens.

1. A METHOD OF MAKING A HEAT EXCHANGER HAVING OPPOSITE SIDES FORADMITTING AND DICHARGING A FIRST FLUID SUCH AS AIR, SAID METHODCOMPRISING FORMING WIDE PORTIONS ALTERNATING WITH NARROW STRIPS ALONG ALENGTH OF SHEET METAL, THE SAID FORMING INCLUDING HOLDING PERIPHERALMARGINS OF ALTERNATE PAIRS OF SAID WIDE PORTIONS IN THE FLAT ANDPRESSING THE METAL ENCLOSED BY SAID MARGINS OF SAID ALTERNATE PAIRS INTORIDGES PROTRUDING FROM ONE SIDE OF SAID SHEET AND INTO RIDGES ALSO ONSAID ONE SIDE AND EXTENDING ENTIRELY ACROSS THE OTHER PAIRS OF SAID WIDEPORTIONS, FORMING OPENINGS DEFINED BY PERIPHERAL FLANGES IN EACH OF SAIDWIDE PORTIONS, FOLDING AND COMPRESSING SAID SHEET WITH FOLD LINES WITHINSAID NARROW STRIPS INTO ZIGZAG FORMATION WITH THE RIDGES AND PERIPHERALFLANGE OF EACH WIDE PORTION OF AN ALTERNATE PAIR INTO FACING RELATIONWITH THE RIDGES AND PERIPHERAL FLANGE OF THE ADJACENT WIDE PORTION OFSAID ALTERNATE PAIR, SECURING THE PERIPHERAL FLANGES OF EACH PAIR OFALTERNATE WIDE PORTIONS TOGETHER, AND SAID METHOD INCLUDING THE REMOVALOF SHEET METAL FROM EACH OF SAID NARROW STRIPS CONNECTING THE WIDEPORTIONS OF THE ALTERNATE PAIR TO AN ADJACENT WIDE PORTION TO OPEN THEGROOVES FROMED BY CORRESPONDING RIDGES.